Great observations. I've always enjoyed this episode and the banter between Dr. Kepple and Columbo. The way Columbo gets under his skin and i like the concept of subliminal messages ( i think i learned about this in high school in the 80's and the concept always intrigued me )

I agree Kepple had to get lucky with the timing of when he thought Norris might go to the drinking fountain. I wonder if there was a Plan B?

Maybe more comments to follow after i read over your observations again.

I know Dr. Kepple used a calibration converter (this episode is the first i had ever heard of this- and i've watched a lot of crime shows...i guess i was naive ) but i wondered why he wouldn't use a silencer as i'm sure the people in the theater would have heard the gunshot from the lobby; and when he shot the projectionist, the audience must have heard also.